The Giants Castle Mountain Hut is located along a footpath at an altitude of 7542ft beneath Giants Castle peak in the central KwaZulu-Natal Ukhahlamba Drakensberg. In 2009 the hut was destroyed by fire and remains in a state of disrepair. A recent decision was taken to rebuild the hut. It’s location in a UNESCO World Heritage Site meant that all building materials, even sand, would have to be brought in. Without road access rebuild planners were faced with a dilemma; besides using donkeys, the only option to deliver materials to the site was by helicopter. On hearing about the project a Johannesburg based helicopter company, Ulitimate Heli, stepped in to help transport the material as part of their commitment to community involvement.
With air cargo work, if the helicopter is large enough cargo can be carried onboard; alternatively a helicopter underslung load is the best method. Slinging, as it is commonly known, is an uncommon practice in South Africa, used by a select few local helicopter operators. Flying an underslung load requires an experienced pilot and ground crews especially if the load is an irregular shape. The job becomes a lot more challenging when operating at altitude in mountainous terrain with the temperamental weather and winds often associated with these environments. The total weight of Giants Castle lift was 3275 kg’s.
Not a great deal for the helicopter, a Airbus Helicopter AS350B3+, which was selected for the task by Ultimate Heli’s team handling the lift. The AS350B+ has a underslung lifting capacity of up to 1400kg at low altitude and is renowned for its capabilities at high altitude. According to Shaun Roseveare, CEO of Ultimate Heli, “load weights for the Giants lift ranged from 300-620 Kg’s, well within the capabilities of the AS350B3+ at the altitudes and temperatures we were operating at, but the physical sizes of some of the loads were quite challenging” Giants Camp is at 5767ft, with the hut site at 7542ft necessitating a climb of 1945 ft while slinging the cargo over a distance of 8,09 km.
The highest altitude reached was 8100ft. The AS350B3+ holds the record for the highest altitude landing – Mt Everest peak 26’000ft in 2005. Preparation of the cargo is important and upon arrival at the site the crew: David Simelane, Shaun Roseveare, Donovan Foley with volunteer Pat Svendsen’s help, arranged the building materials into workable load weights and sizes – eight load types – to ensure that they maximised each load within the operation limits of the helicopter, “taking into account temperature, altitude and wind direction/s.” External loads are categorised as high density, low density or aerodynamic. A high-density load will be stable while the low density will be decidedly unstable. The aerodynamic load may exhibit both characteristics. “We studied each load carefully to determine which description best suit it, and then estimated how it would probably fly,” said Roseveare.
According to Foley, who acted as ‘the eyes’ on the lifts, relaying vital load information back to sling pilot David Simelane: “It’s usually the weight of the load that takes consideration. In this case, however, it was the airborne characteristics, due to the shape of the cargo, which took most thought.” Rigging is a very important element of slinging and time was taken to correctly prepare, weigh and securely rig each load. An afternoon and the following morning were earmarked for the lift. The Ultimate Heli crew, aware of the unpredictable mountain weather planned to complete the lift on the first day if possible. The cargo included a generator and power tools, sand, cement, 6.5m x 1.25 roof trusses, 6.6m wooden batons, roofing tiles and flashing.
Due to the different cargo sizes and weights some intricate planning was needed to find the most suitable material/weight/sling combinations to move all the material safely and efficiently. “We broke the loads down into eight loads.” Cargo nets were used for some items while a simple sling combination was used for others such as the 6.6m wood batons. The crew elected to use a 50ft line as opposed to the 100ft they usually use in remote areas in Africa. The flight route was carefully selected: “We chose a valley, leading to the site to give us maximum clearance under the load and for the helicopter to climb steadily from 5767 ft to 7542 ft.
Always ensuring we had more than 500ft ground clearance under the load in case we needed to ’emergency release’ the load safely and timeously.” With safety always in mind Roseveare was pleased to use a football field to load from. “When lifting the loads we had sufficient open space to hover directly over each load while picking it up into wind which provides the most stable hover.” The crew found that speeds of between 30-60 knots were best suited for these underslung loads: “Flying the heavier loads – 620 Kgs of cement and sand – was quite standard since we used cargo nets which made them stable loads. However, flying the roof trusses was quite a challenge and we needed to pay careful attention to the “flying characteristics ” of the load (roof trusses develop slight aerodynamic effects and develop airfoil properties with the moving air passing over them).
When load oscillations began airspeed was smoothly reduced to establish the maximum safe flying speed for the type of load. Control inputs needed to be gentle and smooth. Reducing collective (and thereby airspeed) and entering a shallow bank was effective in reducing the load oscillations. The main aim of sling pilot David Simelane is to get the sling load moving underneath the helicopter in a synchronised form – this is not always possible with an aerodynamic load. According to Roseveare, “We operated all approaches to the drop off site into wind to preclude the possibility of entering a situation where there is insufficient power available to arrest the descent. A gradual descending approach slightly steeper than normal was used to ensure that we cleared any obstacles with the load. Ground crews at the drop site talked us into each load release location.”
Highlights of the job says Roseveare, “were bringing skills we’ve learnt working in Africa home to put to good use on a rewarding community involvement project like this. Especially in a UNESCO world heritage site. And being one of only three helicopters – besides police search & rescue – in the past five years to fly at Giants.” The team completed the entire lift within four hours. A few days later, while the builders were still on site, it snowed. – See more at: http://ultimate-aviation.net/press-ultimate-heli.html#.VS4Z9hOUfZ0